Some of the Sun’s Iconic Coronal Loops Maybe Mirages


The sun is one of the oldest stars known to date. The Milky Way galaxy itself is about 12 billion years old, meaning this was one of the very first stars to be born in it, maybe even as the galaxy itself was forming. Each planet in our solar system revolves on an axis around the sun. The sun is a very important object in our solar system. Not only does the sun help the Earth stay warm, but it also helps the Earth stay a habitable planet. Coronal loops have been used to measure many properties of the corona, including temperature and density, and they may be key to figuring out why the sun’s atmosphere is so much hotter than its surface.

Some of the coronal loops may be an illusion created by “wrinkles” of greater density in the coronal veil. Solar physicist Anna Malanushenko and her colleagues attempted to isolate individual coronal loops in 3-D computer simulations originally developed to simulate the life cycle of a solar flare. The team expected to see neatly oriented strands of plasma, because coronal loops appear to align themselves to the sun’s magnetic field, like metal shavings around a bar magnet. After the test, Anna Malanushenko said that the plasma appeared as curtain-like structures winding out from the sun. In the simulation, many of the supposed coronal loops turned out to not be real objects.

While there were structures along the magnetic fields, they were neither thin nor compact as expected. They more closely resembled clouds of smoke. As the team changed the point of view from which they looked at these wrinkles in the veil in the simulation, their shape and orientation changed. And from certain viewing angles, the wrinkles resembled coronal loops. “The observations were mind-blowing,” say’s Malanushenko. The structure in the simulation was much more complex and displayed complicated boundaries and a raggedy structure.

Not all coronal loops are in the coronal veil necessarily. “We do not know which ones are real and which ones are not,” Malanushenko says. “And we absolutely need to be able to study the solar atmosphere.”